Magnetic bubble memories as well as the "major-minor" organization of such memories are well known in the art as is disclosed in U.S. Pat. No. 3,618,054 of P. I. Bonyhard, U. F. Gianola, and A. J. Perneski, issued Nov. 2, 1971.
The major-minor organization is characterized by a set of closed "minor" loops in which bubble patterns are recirculated synchronously in response to a magnetic field reorienting cyclically in the plane of bubble movement. The bubbles in each loop are moved through a transfer position which couples a minor loop to a stage of an accessing loop called the major loop. An electrical conductor couples all the transfer positions and is operative, when pulsed, to transfer the bubble pattern, occupying all the transfer positions, into the major loop for movement to a detector. The transfer operation from a minor loop to a major loop is commonly referred to as a "transfer out" operation and results in vacancies in those positions in the minor loops from which the transferred bubble pattern originated.
A bubble generator, on the other hand, provides a bubble pattern for movement into those vacancies. The generator is coupled to the major loop and is operative, responsive to sequence of input signals, to enter a replacement bubble pattern into the major loop. The major loop also is responsive to the cyclical field to move bubbles. Consequently, an input signal during each cycle of the field results in a bubble pattern moving in the major loop towards the transfer positions as the vacancies move in the minor loops toward the transfer positions. An appropriately timed transfer operation moves the replacement bubble pattern into the vacancies. The major-minor organization is useful primarily to decrease the latency time and access time of "field access" type bubble memories which are characterized by a reorienting "in plane" field as described hereinbefore.
Another type of magnetic bubble memory employs electrical conductors rather than a reorienting in-plane field to effect bubble propagation. In the past, conductor access type bubble memories including discrete electrical conductors which could be pulsed selectively to produce bubble movement. There was no need for the major-minor organization in this type of memory. In my copending application Ser. No. 914,959, filed June 12, 1978, on the other hand, no discrete conductors exist; and yet a major-minor organization is particularly attractive. Consequently, a transfer gate is necessary. But no discrete conductors are present to implement a transfer gate. The problem, then, to which the present invention is directed is to provide a transfer gate compatible with the memory disclosed in my above-mentioned patent without employing any additional electrical conductors.